The Combination of Random Mutagenesis and Sequencing Highlight the Role of Unexpected Genes in an Intractable Organism

A large variety of organisms are capable of synthesizing hard matter in a process called biomineralization [1]. The transfor-mation of a genetic blueprint into minerals such as, for example, calcium phosphate in bones and calcium carbonate in eggs or seashells provides a mechanical support for organismic growth and protection against predators, respectively. Iron oxides formed by fishes and birds provide them with magnetic properties used for magne-toreception and orientation [2,3]. The biomineralization processes are remark-able for numerous reasons: organisms, contrary to engineers, have to form these biological materials with a limited subset of biologically available chemical ele-ments and at physiological conditions. Still, these reduced means are not at the detriment of their function, which often surpasses man-made materials based on equivalent elements [4]. Therefore, un-derstanding how biomineralizing organ-isms process chemical elements based on their genetic program is of primary interest. However, the biological mecha-nisms behind biomineralization have re-mained unclear, partly because of limited genetic knowledge: model organisms are limited to a few unicellular organisms [5,6]. Therefore, the question has arisen of what genetic approach to use to get genetic information about the large ma-jority of organisms that have remained intractable

Biosynthesis of magnetic nanostructures in a foreign organism by transfer of bacterial magnetosome gene clusters

The synthetic production of monodisperse single magnetic domain nanoparticles at ambient temperature is challenging. In nature, magnetosomes--membrane-bound magnetic nanocrystals with unprecedented magnetic properties--can be biomineralized by magnetotactic bacteria. However, these microbes are difficult to handle. Expression of the underlying biosynthetic pathway from these fastidious microorganisms within other organisms could therefore greatly expand their nanotechnological and biomedical applications. So far, this has been hindered by the structural and genetic complexity of the magnetosome organelle and insufficient knowledge of the biosynthetic functions involved. Here, we show that the ability to biomineralize highly ordered magnetic nanostructures can be transferred to a foreign recipient. Expression of a minimal set of genes from the magnetotactic bacterium Magnetospirillum gryphiswaldense resulted in magnetosome biosynthesis within the photosynthetic model organism Rhodospirillum rubrum. Our findings will enable the sustainable production of tailored magnetic nanostructures in biotechnologically relevant hosts and represent a step towards the endogenous magnetization of various organisms by synthetic biology